Methods and Means for Installing, Maintaining and Controlling a Self-Standing Riser System

ABSTRACT

Improved systems and methods for installing, maintaining and controlling a self-standing riser (SSR). SSRs are installed using wire pulleys or weights to place the SSRs over a wellhead. A flow diverter, which may be incorporated into or separate from a buoyancy chamber, allowing diversion of flow both into and out of an SSR. Non-annular buoyancy chambers configured to receive a riser of an SSR through a slot of the buoyancy chamber.

FIELD

The present invention relates generally to oil and gas exploration and production systems, and in a plurality of specific though non-limiting embodiments, to various methods and means for installing, maintaining and controlling a self-standing riser system.

BACKGROUND

In recent years, there has been an increasing worldwide demand for oil and gas. Despite exploration and development, oil and gas supply continues to fall short of demand. In an effort to balance supply and demand, companies and governmental entities have begun to explore and develop relatively marginal fields in the deeper offshore waters (e.g., Gulf of Mexico, West Africa and Brazil). Notwithstanding these efforts, due to high construction costs and limited manufacturing facilities, only a small number of mobile offshore drilling units (MODUs) are being manufactured each year, thereby resulting in escalating “per day” unit costs and a shortage of associated offshore drilling, completion and work-over equipment.

As an alternative to MODU production, self-standing riser (SSR) systems may be safely and reliably installed in communication with a well head or production tree. Such risers are self-supporting, and provide all of the risers, casing, buoyancy chambers, etc., necessary for exploration and production and of oil, gas and other hydrocarbons. SSRs also provide the safety features required to ensure that the produced hydrocarbons do not escape from the system out into surrounding waters.

Although SSR systems provide substantial advantages for the production of hydrocarbons, known SSR systems are still difficult to install, maintain, and control, requiring either a number of different surface vessels or a MODU. Often, expensive hull and deck modifications have to be made for installations. Few improvements in associated per-day costs have been realized over non-SSR production.

Accordingly, there is need for more cost-effective means, systems and methods of installing, maintaining and controlling SSR systems.

SUMMARY

In an example embodiment of the present disclosure, a method of installing a riser of a self-standing riser system is provided, including: placing the riser above a wellhead; and attaching the riser to the wellhead; wherein the riser is placed above the wellhead using at least one of a weight attached to the riser and at least one pulley wheel attached to the wellhead. Two pulley wheels may be attached to the wellhead. Two wires may be attached to the riser and passed through the two pulley wheels such that the riser is pulled down by the two wires. The method may include pulling upward on leading ends of the two wires such that the riser is pulled downward via trailing ends of the two wires. The weight may be attached to a top portion of the riser. The weight may be a drill collar. The weight may be attached to a bottom portion of the riser. The weight may be a piece of steel configured to rest upon the wellhead.

In an example embodiment of the present disclosure, a flow diverter is provided, including: a flow diversion path having a first end connected to a riser of a self-standing riser; and a fluid line connected to a second end of the flow diversion path. The flow diversion path is configured to divert fluid flow into and out of the riser. The flow diversion path may be incorporated into a buoyancy chamber. The flow diversion path may be incorporated into a flow diverter device. The flow diverter device may be configured to connect to the riser at a point below a buoyancy chamber.

In an example embodiment of the present disclosure, a buoyancy chamber assembly for a self-standing riser is provided, including: a non-annular chamber having: an outer circumference; an inner circumference forming an opening; and a slot; a hang off ring having: an outer circumference; and a riser space. A diameter formed by the outer circumference of the hang off ring is greater than a diameter of the opening formed by the inner circumference of the chamber. The hang off ring is configured to attach to a riser. The hang off ring is further configured to rest upon a top portion of the chamber. The chamber may have a non-adjustable buoyancy. A width of the slot may be greater than the diameter of a riser installed in the buoyancy chamber assembly. The hang off ring may be configured to hold the riser to the chamber.

DESCRIPTION OF DRAWINGS

FIG. 1 is side view representation of a riser being installed on a wellhead, according to an exemplary embodiment of the present invention.

FIG. 2 is side view representation of a riser installed on a wellhead having a weight on an upper portion of the riser, according to an exemplary embodiment of the present invention.

FIG. 3 is side view representation of a riser installed on a wellhead having a weight on a lower portion of the riser, according to an exemplary embodiment of the present invention.

FIG. 4 is a side view representation of a flow diverter connected to a riser and a production line, according to an exemplary embodiment of the present invention.

FIG. 5 is a side view representation of a buoyancy chamber having a flow diverter, according to an exemplary embodiment of the present invention.

FIG. 6 is a top view of a buoyancy chamber, according to an exemplary embodiment of the present invention.

FIG. 7 is a top view of a buoyancy chamber and a hang off ring, according to an exemplary embodiment of the present invention.

FIG. 8 is a side view of a buoyancy chamber and riser, according to an exemplary embodiment of the present invention.

FIG. 9 is a side view of a riser having a hang off ring, according to an exemplary embodiment of the present invention.

DESCRIPTION

Embodiments of the present invention provide improved methods and systems for installation, maintenance and control of SSRs. In example embodiments of the present invention there is provided improved systems and methods for installation of an SSR upon a wellhead. Embodiments of the present invention incorporate pulleys to pull an SSR into place over a wellhead. Embodiments of the present invention may include two or more sheeves attached to a wellhead and configured such that wires attached to a connector of a riser may be passed over said sheeves as the connector is pulled down over the wellhead. Embodiments of the present invention may include one or more surface wenches connected to the wires. Alternate embodiments of the present invention may include a weight connected to a either a top portion of an SSR system or a bottom riser of said system. The weights may be used to lower the SSR into place and the weights may be removable after installation. Embodiments of the present invention may include a flow diverter device which may be part of a buoyancy chamber or may be separate from the buoyancy chamber. In example embodiments, the flow diverter device may be configured to divert flow both into and out of an SSR. Embodiments of the present invention include a non-annular buoyancy chamber which may be used with rigid and/or flexible risers. Embodiments of the non-annular buoyancy chamber may have a slot on a side of the chamber configured to allow a riser to be slipped into an inner circumference of the chamber. Embodiments may include a hang off ring which may be attached to a top portion of a riser and may be configured to rest upon the chamber when the riser is placed within the chamber. In example embodiments, the buoyancy chamber may have little or no buoyancy adjustability.

Referring to the exemplary embodiment of the present invention shown in FIG. 1, there is provided a system and method of installing a riser 20 over a wellhead 10 at sea floor 30 via wires 120. As shown, a pair of pulley wheels 130, which may be sheeves, are attached to a base of wellhead 10. Riser 20 has a connector 100 which is connected to wires 120 via connector rings 110, which may be any type of attachments suitable for connecting wire 120 to connector 100. Riser 20 is installed over wellhead 10 by pulling upward on leading end 140 of wire 120 such that wire 120 is pulled over the pulley wheels 130 and trailing end 150 of wire 120 diminishes. Leading end 140 may be pulled upward via one or more surface wenches. Although shown with two wires 120 and two pulley wheels 130, more or less pulley wheels 130 may be attached to wellhead 10 and installation may use all of the pulley wheels 130 or less than all of the pulley wheels 130. The SSR may have a pre-set buoyancy allowing the risers to be under proper tension as the SSR is pulled down over the wellhead. Once pulled sufficiently down over the wellhead, the SSR may be attached to the wellhead.

In FIGS. 2 and 3, alternative embodiments of the present invention are shown wherein weight 200 is used to lower riser 20 of the SSR over wellhead 10. Weight 200 may by attached to a top portion of riser 20 such that it pushes riser 20 downward. See, e.g., FIG. 2. Weight 200 may be a drill collar which may be removed after riser 20 is installed. Riser 20 may have slightly positive buoyancy distributed across riser 20 providing tension along the length of riser 20. Alternatively, weight 200 may be attached to a bottom of riser 20, pulling 20 downward. See, e.g., FIG. 3. Weight 200 may be a piece of steel and may be configured to land upon wellhead 10. When in contact with wellhead 10, weight 200 will have a neutral effect on the riser 20. Slightly positive buoyancy may be distributed across riser 20 which may provide tension along the length of riser 20.

In example embodiments of the present invention there is provided a flow diverter device 320 which may be used to divert flow both into and out of riser 20. See, e.g., FIG. 4. Flow diverter device 320 may be below buoyancy chamber 50. Alternatively, flow diversion path 330 may be incorporated into buoyancy chamber 50. See, e.g., FIG. 5. As shown in FIG. 4, production flow from wellhead 10 and production tree 40 may pass upwards through riser 20 and into flow diversion path 330 of flow diverter device 320. Flow may be directed from the flow diversion path 330 to a production vessel via production/injection line 310.

Buoyancy chamber 50 may have annular space 300. Flow diversion path 330 may be used for hydrocarbon production, fluid injections, or any combination of the two. Flow diversion path 330 may be located in flow diverter device 320 or integral to buoyancy chamber 50.

In further embodiments of the present invention there is provided buoyancy chamber 400 having slot 430 configured to receive a riser. See, e.g., FIGS. 6 to 8. Buoyancy chamber 400 may be non-annular. Except for slot 430, buoyancy chamber 400 has an outer circumference 410 and an inner circumference 420. A diameter formed by inner circumference 420 may be configured to be larger than a diameter of a riser to be installed therein. Buoyancy chamber 400 may be non-adjustable and may be configured to rest at the water surface 60 when riser 480 is installed therein. See, e.g., FIG. 8. Embodiments may include hang off ring 440 having an outer circumference 450 and an inner circumference 460, which forms riser space 470. A diameter formed by outer circumference 450 is substantially larger than the diameter formed by inner circumference 420 such that hang off ring 440 rests upon buoyancy chamber 400 when installed thereon. Hang off ring 440 may be attached to an upper portion of riser 480. See, e.g., FIG. 9. When installed, hang off ring 440 rests upon buoyancy chamber 400 holding riser 480 in place. Riser 480 may be installed into buoyancy chamber 400 by sliding riser 480 into slot 430. Alternatively, riser 480 may be installed into buoyancy chamber 400 by passing riser 480 through inner circumference 420. Riser 480 may be under tension when installed and may be lowered until hang off ring 440 rests upon buoyancy chamber 400. Riser 480 may be rigid or flexible. A surface vessel may be used to tension riser 480 and then lower it down inside buoyancy chamber 400, releasing the weight of riser 480 to the buoyancy chamber 400.

Embodiments of the present invention include installation methods, flow diversion apparatuses and non-annular buoyancy chambers which may be used in combination for efficient installation, maintenance and control of a SSR.

While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventions is not limited to them. Many variations, modifications, additions, and improvements are possible. Further still, any steps described herein may be carried out in any desired order, and any desired steps may be added or deleted. 

What is claimed is:
 1. A method of installing a riser of a self-standing riser system, comprising: placing the riser above a wellhead; and attaching the riser to the wellhead; wherein the riser is placed above the wellhead using at least one of a weight attached to the riser and at least one pulley wheel attached to the wellhead.
 2. The method of claim 1, wherein two pulley wheels are attached to the wellhead.
 3. The method of claim 2, further comprising two wires attached to the riser and passed through the two pulley wheels such that the riser is pulled down by the two wires.
 4. The method of claim 3, further comprising: pulling upward on leading ends of the two wires such that the riser is pulled downward via trailing ends of the two wires.
 5. The method of claim 1, wherein the weight is attached to a top portion of the riser.
 6. The method of claim 5, wherein the weight is a drill collar.
 7. The method of claim 1, wherein the weight is attached to a bottom portion of the riser.
 8. The method of claim 7, wherein the weight is a piece of steel configured to rest upon the wellhead.
 9. A flow diverter, comprising: a flow diversion path having a first end connected to a riser of a self-standing riser; and a fluid line connected to a second end of the flow diversion path; wherein the flow diversion path is configured to divert fluid flow into and out of the riser.
 10. A flow diverter of claim 9, wherein the flow diversion path is incorporated into a buoyancy chamber.
 11. A flow diverter of claim 9, wherein the flow diversion path is incorporated into a flow diverter device.
 12. A flow diverter of claim 11, wherein the flow diverter device is configured to connect to the riser at a point below a buoyancy chamber.
 13. A buoyancy chamber assembly for a self-standing riser, comprising: a non-annular chamber having: an outer circumference; an inner circumference forming an opening; and a slot; a hang off ring having: an outer circumference; and a riser space; wherein a diameter formed by the outer circumference of the hang off ring is greater than a diameter of the opening formed by the inner circumference of the chamber; wherein the hang off ring is configured to attach to a riser; and wherein the hang off ring is further configured to rest upon a top portion of the chamber.
 14. The buoyancy chamber assembly of claim 13, wherein the chamber has a non-adjustable buoyancy.
 15. The buoyancy chamber assembly of claim 13, wherein a width of the slot is greater than the diameter of a riser installed in the buoyancy chamber assembly.
 16. The buoyancy chamber assembly of 13, wherein the hang off ring is configured to hold the riser to the chamber. 